1. Field of the Invention
The present invention relates to fluid control valves, and more particularly to pressure actuated valves for fuel injectors employed with gas turbine engines.
2. Description of Related Art
Pressure actuated valves are well known in the art, and one example is a valve assembly used in a fuel system to provide specific flow rates as a function of pressure. One particular application of such valves is in fuel injector systems of gas turbine engines.
It is well known that in fuel supply systems of gas turbine engines, for example, it is desirable when the engine is shut down to preclude flow of even small amounts of fuel to the nozzles that deliver fuel to the combustion chamber. It is also desirable to open valves to provide an initial flow of fuel from the reservoir to the engine when a relatively low pressure differential exists between the reservoir and the engine, as during engine start up. In many applications, it is also desirable to meter the amount of fuel supplied to the engine when the engine is operated under load, by opening a second, variable-rate flow path when the pressure differential exceeds a predetermined value.
In the past, it has been customary for these two functions, namely the check valve and metering valve functions, to be performed by two substantially independent valve assemblies. However, the use of two separate valve assemblies results in increased cost and weight, increased use of space and increased opportunities for malfunctions to occur among the multiple components that are required.
Valves have been constructed in which the functions of check valve and metering valve are combined into a single multi-port valve assembly. Typical valves of this type have relied on combinations of separate metering valves and check valves, resulting in relatively large part counts and weights. Other valves have incorporated pressure actuated designs having a combined, multi-port valve assembly that is more compact, requires fewer parts and is lighter in weight than the conventional combined valves.
Depending on the design and the joining methods used, it can be difficult to achieve a high degree of precision during assembly of previously known multi-port valves. Imprecise assembly can result in significant deviations between actual valve performance and desired valve performance. For example, if valve parts are welded or brazed during assembly, thermal expansion or other distortions arising during the welding process can render precision features designed into the valve assembly inoperative.
While the conventional systems and methods have generally been considered satisfactory for their intended purposes, there still remains a continued need in the art for valve assemblies having improved precision and performance. There also remains a need in the art for methods of assembling such valves. The present invention provides a solution for these problems.